Albulae Aquae, a group of springs, •4 m. W of Tibur, the water of which is bluish, strongly impregnated with sulphur and carbonate of lime, and rises at a temperature of •about 75° F. Remains of a Roman thermal establishment exist near the principal spring, the so‑called Lago della Regina (which is continually diminishing in size owing to the deposit left by the water), and dedicatory inscriptions in honour of the waters have been found. The baths are still frequented by the Romans, though the modern establishment is •about 1 m. S on the high road.

See T. Ashby in Papers of the British School at Rome, III.117.

Thayer's Note:

a
Aquae Albulae is mentioned by Pliny
(N.H. XXXI.10),
Strabo
(V.3.11), and Isidore, who gives it pride of place in his section on mineral springs
(Orig.XIII.13), probably because it is so close to Rome; Vitruvius is not interested in its therapeutic qualities, just its sulphureous stink
(VIII.3), commenting that there are a number of other sulfur springs in the area round Rome: as one might expect from a volcanic area, that's quite true, and
from personal experience, they definitely make their presence felt. Less identifiably, Vergil as well mentions a truly ferocious stench from a spring he calls Albunea
(Aen.VII.81), an adjectival form that Varro says was the given name of the Tiburtine Sibyl.

The convenient 21 km distance very likely accounts for its favor with the emperor Augustus, afflicted with bone problems
(Suet. Aug. 82.2); the waters at Bagni di Tivoli are still used today in treating bone diseases, and the area boasts in consequence several luxury hotels: for a good overview, see this
unofficial Bagni di Tivoli site, with many photos, including one of the remains of a 1c Roman tomb attributed to M. Plautius Lucanus.

Another selling point of these waters was the oracle of Faunus at the springs; for details, see the article
Oraculum
in Smith's Dictionary of Greek and Roman Antiquities.

Images with borders lead to more information.
The thicker the border, the more information.
(Details here.)